Mineral specimen boxes and stands
Conservation guidance names clear polystyrene boxes, low-acid card trays, acid-free tissue and Plastazote. The enclosure follows the species, not the budget.
Published conservation guidance is specific: store each mineral specimen in a clear polystyrene lidded box or a low-acid card tray, nested in acid-free tissue or a Plastazote cut-out, at 45 to 60% relative humidity. Light-sensitive species go in light-proof containers. The enclosure follows the crystal, not the budget.
In short
- There is real published guidance on this, and most collectors have never read it. The NatSCA and Icon leaflet on geological collections names the materials by name: clear polystyrene lidded boxes, low-acid card trays, acid-free tissue, Plastazote.
- Clear lids are recommended for a reason that is not aesthetic. They let the specimen be seen without being handled, and handling is where most damage happens.
- Four groups of species need something other than the default. Light-sensitive species need opaque boxes; pyrite-bearing material needs a sealed box with dried silica gel; hydrated species need not to be dried; toxic and radioactive species need lids regardless of what else is true.
- Stands are a display problem, not a storage problem, and the failure mode is different: a specimen that rocks on a stand will eventually be knocked off it. Support the centre of mass, not the prettiest angle.
- Buy the enclosures before you buy more specimens. Storage bought after the fact is always a compromise, and specimens waiting for it are specimens at risk.
| The specimen | Enclosure | Padding | Why | Source of the requirement |
|---|---|---|---|---|
| Ordinary stable material | Clear polystyrene lidded box or low-acid card tray | Acid-free tissue or Plastazote cut-out | Dust protection; visible without handling | NatSCA/Icon leaflet |
| Light-sensitive: realgar, other arsenic sulphides, amethyst, green fluorite | Light-proof container | As above | Realgar converts irreversibly to a powdery orange para-realgar; amethyst and green fluorite fade | NatSCA/Icon leaflet |
| Pyrite- or marcasite-bearing | Well-sealed box, or specimen sealed in Escal film | Plastazote cut-out plus a pierced bag of oven-dried silica gel | Holds the interior below the humidity at which iron sulphide decays | NatSCA/Icon leaflet |
| Hydrated species: torbernite, chalcanthite | Sealed box without desiccant | Plastazote | These lose water and change species or crumble in dry air | Handbook of Mineralogy; NatSCA/Icon leaflet |
| Toxic: arsenic, antimony, soluble lead such as cerussite | Lidded clear polystyrene box, lined | Plastazote | Contains dust; labelled hazard stays with the specimen | NatSCA/Icon leaflet |
| Radioactive | Lidded box, stored away from occupied rooms | Plastazote | Contains dust carrying radon decay products | NatSCA/Icon leaflet |
| Fragile: crocoite, reticulated cerussite, acicular sprays | Rigid lidded box, deep enough for clearance | Cut cavity supporting the matrix only | Nothing should touch a crystal | Habit and tenacity of the species |
What the conservation guidance actually says
The reference document for a British collector is the NatSCA and Icon leaflet Care and Conservation of Geological Specimens. It is four pages and free, and it is more specific than most of what is written about specimen storage.
On enclosures it says: specimens can be stored in clear polystyrene lidded boxes, or low-acid card trays, nested in acid-free tissue or Plastazote cut-outs, and that clear lidded boxes provide protection from dust and allow the specimen to be seen, reducing the need for handling it.
On the room it says: 45 to 60% relative humidity, and a temperature as stable as possible, ideally a constant 16 to 18 degrees C and certainly between 10 and 22 degrees C. It also says to keep specimens out of direct sunlight and limit other light sources.
Two specific exceptions follow. Pyrite-containing specimens should not be stored above 60% RH and preferably at 45% or lower. Light will irreversibly damage some species, and the leaflet names the arsenic sulphides — realgar in particular, which converts to a powdery orange para-realgar — along with amethyst and green fluorite; susceptible species should be stored in light-proof containers.
None of this requires expensive equipment. It requires choosing the box on the basis of what is in it, which is the part most collectors skip.
The enclosure follows the species, not the budget
The default — a clear lidded box with a Plastazote cut-out — is right for most of a collection. The decision that matters is recognising the specimens for which it is wrong.
Light-sensitive species need an opaque box even though a clear one is nicer. That is not a preference, it is the difference between a realgar and a heap of orange powder. Our page on which minerals fade in light lists the species involved.
Iron sulphides need the box sealed and dried. The leaflet describes the method precisely: place the specimen in a well-sealing box, pack it in a Plastazote cut-out, and add a small pierced zip-lock bag of oven-dried silica gel, which will remove moisture from the interior. It notes that a sealed environment can also be created by sealing the specimen inside Escal film. The reason is on why pyrite crumbles.
And a few species need the opposite treatment. Torbernite’s water content varies with relative humidity and it dehydrates to metatorbernite in dry air; chalcanthite crumbles to a pale blue powder below 35% RH. Putting either in a desiccated box damages it. The point is not that any one number is right; it is that a collection is not one environment. The species-by-species case is on torbernite.
Stands: what they are for and how they fail
A stand is display furniture. It does nothing for preservation and it introduces a risk the box does not, which is that a specimen on a stand can fall off it.
Three rules cover most of it. Support the centre of mass rather than the best viewing angle. A specimen tilted to show its face and balanced on one corner is a specimen waiting for a door slam. Nothing rigid should touch a crystal. Acrylic cradles, brass easels and wire stands all bear on a point, and a point load on a soft or brittle species is a bruise. And a stand should not need adhesive. Museum putty is reversible in principle and stains porous material in practice; if the specimen needs sticking down to stay upright, it needs a different stand.
For heavy species the arithmetic is worth doing. Cerussite has a density of 6.55 and crocoite 6.0 to 6.1, so a specimen the size of a fist is carrying two to three times the weight your hand expects, on crystals at hardness 3 or below. That combination is why cabinet accidents disproportionately involve heavy lead minerals.
Where a specimen goes, and how much light it will accumulate on a shelf compared with a closed cabinet, is worked out on how to display a mineral collection.
Practical choices, and where the money is worth spending
Buy one size of box and stick to it. A drawer of mixed enclosures wastes more space than any individual choice saves, and it makes the collection hard to search. Standard thumbnail boxes are about 30 mm; miniature trays around 70 mm. The size conventions are on specimen sizes and grading.
Plastazote is worth buying properly. It is a closed-cell polyethylene foam that is chemically stable, and the reason conservation guidance names it rather than “foam” is that many cheap foams are not stable and off-gas as they age. Cut a cavity that supports matrix and leaves air around every crystal.
Do not use cotton wool on anything with fine crystals; the fibres hook on acicular and micaceous species and pull them out. Acid-free tissue is the leaflet’s recommendation and behaves better.
Label the box as well as the specimen. The leaflet makes the point specifically for hazardous material: once identified, appropriate labels should be added to specimen boxes, drawers and cupboards. That applies to the toxic and radioactive drawer above everything else — see toxic minerals in a collection.
The rest of the collecting guides cover handling, cleaning and condition, and if you are looking for particular species and want to be told when we see them, that is the wanted list.